1. Field of the Invention
The present invention relates to a wireless telephone set such as a digital wireless telephone equipment and so forth, which is operable in a power saving mode.
2. Description of the Related Art
FIG. 1 is a block diagram showing a conventional wireless telephone set. In the figure, reference numeral 1 is an antenna for transmitting and receiving electromagnetic wave, and 2 is a duplexer for distributing transmitting high frequency signals to the antenna 1 and for coupling receiving high frequency signals from the antenna 1. Reference numeral 3 is a transmitter for converting a voice electric signal into the afore-mentioned transmitting high frequency signal, and 4 is a microphone for converting a voice into the above-mentioned voice electric signal. Reference numeral 5 is a receiver for converting the above-mentioned high frequency signal into a voice electric signal, and 6 is a speaker for converting the voice electric signal into a voice. Reference numeral 7 is a transmitter-side power switch for turning ON or OFF of the power supplied to the above-mentioned transmitter 3, and 8 is a receiver-side power switch for turning ON or OFF of the power supplied to the above-mentioned receiver 5. Reference numeral 9 is a battery for supplying a power to the whole of this wireless telephone set, and 10 is a main switch for turning ON or OFF of the supply of the power from the battery 9. The above-mentioned transmitting-side power switch 7 and the receiving-side power switch 8 are connected through this main switch 10 to the battery 9.
Further, reference numeral 11 is a reference signal oscillator which directly receives the power supplied from the battery 9 through the main switch 10 to oscillate to generate a reference signal, and 12 is a frequency dividing circuit for dividing the reference signal generated by the reference oscillator 11 to output frame pulses. Reference numeral 13 is a timing generating circuit for controlling the timing of the transmission and the reception by controlling the abovementioned transmitter 3, the receiver 4, the transmitting-side power switch 7, the receiving-side power switch 8, and so forth, and 14 is a timing circuit power switch, connected to the battery 9 through-the main switch 10, for turning ON or OFF of the power supplied to the timing generating circuit 13. Reference numeral 15 is a microprocessor as a control circuit for controlling the frequency dividing circuit 12, the timing generating circuit 13, the timing circuit power switch 14 and so forth, based on the frame pulses outputted from the above-mentioned frequency dividing circuit 12. In this connection, the power supply to the microprocessor 15 is directly effected from the main switch 10.
Next, the operation of the conventional circuit shown in FIG. 1 will be described. When the main switch 10 is turned ON, the microprocessor 15 is supplied with a power to start its operation so as to initialize the frequency dividing circuit 12. After that, during a waiting state for waiting an arriving call to the wireless telephone set under consideration (hereinafter simply referred to as a waiting state), the microprocessor 15 instructs the timing generating circuit 13 to turn OFF the transmitting-side power switch 7 and the receiving-side power switch 8, The microprocessor 15 also turns OFF the timing circuit power switch 14. By this, those which are supplied with the power are three, i.e., the reference oscillator 11, the frequency dividing circuit 12, and the microprocessor 15. The microprocessor 15 determines the type of the frame by counting the frame pulses from the frequency dividing circuit 12 by the software in the microprocessor 15, and when the frame is a control channel for the wireless telephone set under consideration, the timing circuit power switch 14 is turned ON to operate the timing generating circuit 13, so as to instruct the timing generating circuit 13 to turn ON the transmitting-side power switch 7 and the receiving-side power switch 8. Thus, the microprocessor 15 controls the timing generating circuit 13 in accordance with the frame type of each frame.
Since the conventional wireless telephone set is constructed as above, even when it is under a waiting state, it is necessary to always supervise the frames by software in order to receive the control channel at the particular frame timing. Therefore, there is a problem in that a power must be always supplied to the microprocessor 15 even during a waiting state.
In addition, since there is no auxiliary battery in the conventional wireless telephone set, when the battery voltage is lowered due to exhaustion during a call is connected, there is a problem in that the call is disconnected.